Thread monitoring device

ABSTRACT

A SEWING MACHINE ACCESSORY FOR MOUNTING ONTO THE SEWING MACHINE AND THERE MONITORING THREAD TO BE PRESENTED TO THE NEEDLE OF THE MACHINE. THE DIVICE INCLUDES A MODIFIED THREAD GUIDE WHICH SUBSTITUTES FOR THE NORMAL THREAD GUIDE. THE MODIFIED THREAD GUIDE AND THREAD THEREIN COOPERATE FORMING AN ARRESTING COMBINATION FOR A PIVOTALLY MOUNTED BIASED ROD. THE ROD IS BIASED TOWARD ESCAPE FROM ARREST UPON ABSENCE OF THREAD IN THE GUIDE, AND UPON   ESCAPING FROM ARREST THE ROD EFFECTIVELY ACTUATES AN INDICATION DEVICE.

Feb. 6, 1973' G. a. SARAY 3,714,916

THREAD MONITORING DEVICE Filed March 27, 1968 v .z'sheeis-sheet 1 Feb. 6, 1973 s. B. SARAY 3,714,916

THREAD MONITORING DEVICE Filed March 27, 1968 2 Sheets-Sheet 2 United States Patent 3,714,916 THREAD MONITORING DEVICE George B. Saray, New Fairfield, Conn., assignor to Ivanhoe Research Corporation, New York, N.Y. Filed Mar. 27, 1968, Ser. No. 716,604 Int. Cl. D05b 51/00 US. Cl. 112--218 R 1 Claim ABSTRACT OF THE DISCLOSURE A sewing machine accessory for mounting onto the sewing machine and there monitoring thread to be presented to the needle of the machine. The device includes a modified thread guide which substitutes for the normal thread guide. The modified thread guide and thread therein cooperate forming an arresting combination for a pivotally mounted biased rod. The rod is biased toward escape from arrest upon absence of thread in the guide, and upon escaping from arrest the rod effectively actuates an indication device.

The present invention relates to thread monitoring or thread presence detection devices. The device herein shown and described has its principal use as an attachment or accessory for a sewing machine, such as a lock stitch sewing machine, for example.

Generally the present invention is a device which continually monitors the presence of thread passed through the device and presented to the needle of a sewing machine. Some thread detectors which are used in various types of sewing machines detect and sense one or more active characteristics associated with the thread used with the sewing machine. For example, some thread sensing devices detect thread by sensing the tension of the thread presented to the needle, as opposed to detecting the thread itself. Other thread sensing devices detect and monitor the travel or drawing speed of the thread as it is drawn or pulled off the spool and presented to the needle. This type of device is essentially a motion detector, as opposed to a presence detection device.

In distinction to other types of thread sensing and thread monitoring devices, the present invention senses the presence of thread without regard to the tension of the thread and without regard to the travel or draw speed of the thread.

The present invention utilizes a thread guide and an inherent characteristic of the thread itself, each cooperating with a biased pivot rod for monitoring the presence of thread just prior to presentation of the thread to the needle of the sewing machine. In addition, the device as shown takes advantage of the action in the thread takeup arm on the sewing machine to remove the thread from the monitoring device when the thread becomes broken between the monitoring device and the needle of the sewing machine.

As one of the cooperating components .a thread guide, normally found on a lock stitch sewing machine, is modified so that the guide itself maintains its normal function as a guide for the thread. In its modified form, the split, spaced eyes of the thread guide serve to receive a biased pivot rod between them. The spacing of the split eyes of the modifiedthread guide is such as to use the natural inherent slight stiffness in the thread to hold the pivot rod between the spaced eyes of the guide, thus essentially employing the thread to arrest the biased pivot rod. With the biased pivot rod in arrested position, presence of thread between the eyes of the guide is positively detected and monitored. When the biased pivot rod escapes from a captive condition, an absence of thread for the needle is indicated, since escape of the biased rod is a function of the absence of thread in the modified thread guide.

3,7143% Patented Feb. 6, 1973 The presence of the thread passing or present between the eyes of the modified thread guide serves as the arresting force for maintaining the biased pivot rod captive, thus avoiding the need of sensing the draw speed or travel of the thread. The dual eyes of the guide are sufiiciently spaced so as to permit uninhibited access of the biased pivot rod therebetween and yet sufliciently closed so as to employ the inherent stiffness in the thread as a restraining or blocking force which serves to complete the arresting action imposed upon the biased rod, thus obviating the need for any thread tension whatsoever.

When released from its captive position the biased rod effectively homes between a pair of open contacts, effectively bridging such contacts and closing an electric circuit for actuating a sensitive device such as a sensitive relay which may serve as a thread break indicator or may serve to open a control circuit for effectively stopping the swing machine.

The biased pivot rod may be biased to escape from arrest by a spring. Preferably, since the biased pivot rod may be an electrical conductor the rod may be formed of a metal material having magnetic characteristics, and under such conditions a magnetic means, such as a permanent magnet or the like, may be used to bias the pivot rod.

It is an object of the present invention to provide a thread monitoring device which monitors the presence of thread presented to the needle of a sewing machine and utilizes the inherent slight stiffness in the thread as a blocking force to effect sustained capture of a biased pivot rod in a thread guide.

Another object is to provide a thread presence monitoring device which uses a modified thread guide cooperating with thread passing through such guide to arrest a biased pivot rod which effectively escapes its capture when thread is absent from the thread guide.

These and other objects will become apparent from reading the following detailed description with reference to the accompanying drawings in which:

FIG. 1 is a pictorial diagram of the preferred form of thread monitoring device illustrated mounted on a sewing machine;

FIG. 2 is an enlarged view of the cooperating arresting components holding the biased pivot rod captive;

FIG. 2a is a cross section of the modified guide, the thread and the pivot rod showing how thread stiffness functions as an arresting force, and

FIG. 3 is an exploded view of the thread monitoring device.

Referring to FIG. 1 part of a sewing machine, such as a lock stitch sewing machine, is shown including the machine head 10. A needle 11 is shown extending from the head on a reciprocating needle bar 12 to which the needle 11 is attached by suitable means. Upon its down stroke the needle passes through a hole 13 in the presser foot 14. This presser foot is coupled to the presser foot bar (not shown) which extends into the head 10. The presser foot bar passes through a sleeve to which the thread monitor mounting box 15 is coupled. In FIG. 3 a hole 16 may be seen in the box 15 and the bushing (not shown) extending down from the head 10 passes through the hole 16. Suitable locking means, such as a lock screw, serve to hold mounting box 15 on the bushing.

The presser foot 14 may be removed from the presser foot bar by loosening the screw 20. The mounting box 15 may then be slid up the presser foot rod and onto the bushing and held in place, as seen in FIG. 1, by suitable means, not shown.

As seen particularly in FIG. 1 an upper thread guide 21 is mounted on the head 10 and guides the thread 22 between the take up arm 23 and the modified lower thread guide 24 The thread 22 then passes to the needle 11. The

thread take up arm 23 reciprocates in phase with the needle 11 thus reducing thread slack as the needle retracts up through the throat plate 25 and the hole 13 in the presser foot 14. This action of the take up arm is well known in the art but is generally discussed here to recall the course and action of the thread.

Directing attention to FIG. 3 as well as FIG. 1, it is seen that the mounting box 15 is enclosed by a plate 30. The plate 30 is illustrated as being transparent and is held in place by two screws 31 and 32. The interior of the box 15 houses a magnetic member 33, a pair of spaced contacts 34 and 35 and a pair of electrical conductors 36a and 37a which connect the respective contacts to respective terminals 36 and 37. The terminals 36 and 37 may be connected into an electric control circuit by a lead or pair of leads represented by lead 38. Preferably the mounting box 15 is made of a non-conductor material, such as a plastic so that the need for additional electrical insulation is avoided.

The biased pivot rod 40 is preferably mounted in a low friction pivot 41. The pivot mount 41, which may be a jeweled pivot, has pointed ends which are seated for low friction action in sockets in the mounting pins 42 and 43 which are adjustable and are locked in place by the nuts 44 and 45 respectively.

The modified thread guide 24 is connected to the mounting box 15 by means of screws 46 and 47.

Referring particularly to FIG. 2, it is seen that the modified guide 24 consists of two spaced eyes which are connected by a U-shaped tongue 48. The tongue 48 is a split structure the end of which bands outwardly so that the rod 40 may pass freely into a captured position between the spaced eyes. The tongue 48 also aids in guiding the thread 22 into the eyes of the guide 24 when the thread is being threaded into the eyes. It will be appreciated that the tongue 48 may be eliminated, if desired.

The plate 30 includes an elongated clearance opening 50 through which the rod 40 extends out of the box 15. When fully assembled and mounted on a sewing machine the modified guide 24 is in correct position to serve and does serve as a guide to guide the thread 22 to the needle 11. The magnet 33 is positioned near the inner end of the pivot rod 40 and serves to bias the pivot rod, which swings arcuately about the pivot 41. A spring may be used to bias teh rod 40, if desired, but a magnetic means is preferable because when the rod 40 is in its captive position the biasing force exerted on the pivot rod 40 by a magnetic means is minimal so that there is relatively little pressure on the thread 22. However, the magnetic means is sufliciently strong and is positioned to provide suificient bias the rod 40, if desired, but a magnetic means is prefersence of thread from the eyes of the guide 24 even though the inner end of the rod is spaced from the magnetic means. In addition, positive contact between the spaced contacts 34 and 35 is made and assured by the strong magnetic attraction of the magnet 33 on the pivot rod 40 'when the rod 40 is close to the magnet 33. The inner end of the rod 40 is of suflicient diameter to more than bridge the space between the contacts 34 and 35. This bridging of the spaced contacts 34 and 35 by the rod may complete an actuating circuit of which the conductor 38 forms a part.

When a sewing machine is in use, a great deal of dust (normally referred to as flufr) develops as a result of working on or with the cloth or fabric material and thread being sewn. In order to keep the fluff out of the thread monitoring device, and particularly to keep the fluff out of the mounting box 15, clean air is blown into box 15 by means of the air tube 55. By blowing clean air into the box 15, air pressure is built up inside box 15, and an air flow is set up which comes out of the opening 50. This prevents the fluff from entering thebox 15. In addition, another air tube 56 is positioned to direct air at the region where the rod 40 is normally held captive. The air tube 56 may be coupled to box 15 so as to obtain air from the inside of box 15.

It will be appreciated that the principles embraced in the preferred form of thread monitoring device shown and described herein may be employed in a device which is modified in structure and arrangement. Although an alternate bias means has been mentioned other changes including rearrangements and substitutes may be made, as will be familiar to those skilled in the art, without dc parting from the spirit of the invention as defined in the appended claim.

What is claimed is:

1. A device for monitoring thread presented to the needle of a sewing machine including;

a housing adapted for mounting on the sewing machine adjacent the needle thereof,

a rod pivotally mounted within said housing having one end thereof extending out of said housing,

thread guide means mounted for positioning adjacent said needle and having spaced eyes for receiving said one end of said rod therebetween, said thread passing through said eyes, said spaced eyes and said thread cooperating for arresting said rod between the said eyes,

contact means associated with said housing adapted for operating a control circuit to indicate the absence of thread,

the other end of said rod being positioned within said housing and being arranged to actuate said contact means when said one end of said rod escapes from arrest,

bias means for urging said rod pivotally against said thread for elfecting escape of said rod in the absence of thread passing through said eyes, and

means for blowing air into said housing to prevent the entry of fluff therein.

References Cited UNITED STATES PATENTS 2,387,369 10/1945 Vossen 112-219 R 2,921,546 1/1960 Vossen 112219 R 3,129,680 4/1964 Doerner 112-218 R 3,255,385 6/1966 Gith ZOO-61.18 2,424,102 7/1947 Le Vesconte et a1. 112-218 R 2,997,557 8/1961 Gillmor et a1. ZOO-61.45 M

H. HAMPTON HUNTER, Primary Examiner US. Cl. X.R. 20061.18 

